Loader-crowding drive



May 24, 1955 A. T. Losus 2,708,800

LOADER-CROWDING DRIVE Filed Aug. 15, 1949 2 Sheets-Sheet 1 REMOTE colvfRoL IN CAB CROWDING 38 FORWARD RATEOF 2 Q q C) f 32 REVERSE 0 I 43 22 AUXILLOARY -49 HYDRAULIC DEvlcEs V ENGINE TRANS- MISSION W/IRIABLE s sso 33 I OIL TANK /WZM May 24, 1955 A. T. LOGUS LOADER-CROWDING DRIVE Filed Aug. 15, 1949 2 Sheets-Sheet 2 DRIVE FOR DIGGING AND CONVEYING MEANS -REMOTE CONTROL DRIVE TO WHEELS United States Patent O LOADER-CROWDING DRIVE Anthony T. Logus, Chicago, 111., assignor to Pettibone Mulliken Corporation, Chicago, 111., a corporation of Delaware Application August 15, 1949, Serial No. 110,316

22 Claims. (Cl. 37190) In removing snow or dirt, present preferred practice is to pile such material along the edge of the road in a windrow and load it into trucks by a loader which moves slowly along the windrow, digging and elevating the material therein as it progresses. One of the most satisfactory forms of loaders includes a few buckets or scrapers carried by endless chains and which move the dirt onto an endless belt conveyor, the latter carrying the dirt upwardly and to the rear where, at the upper end of the belt conveyor, it drops into a truck which has been driven under the conveyor and moves along with the loader until the truck is filled.

For driving the buckets and belt conveyor and for transporting the entire loader at reasonable speed between loading operations, a reasonably powerful internal combustion engine is provided. During the loading operation, however, the vehicle must progress at very slow speed. Practice heretofore has been to include special crowding gears which will drive the traction wheels of the vehicle at a crawling speed while the engine is rotating at eflicient operating speed for driving the buckets and belt conveyor. The result was that the engine was coupled to the traction wheels with an extreme gear ratio capable of applying to the driving shaft of the traction axle torques of terrifically high value. Although the availability of high torque is ordinarily considered quite desirable, something is likely to break when it passes a safe limit. For example, if rotation of the traction wheel is prevented by an obstruction, the extreme torque is capable of twisting off the drive shaft. This has happened on various occasions.

The present invention provides a crowding drive for crowding the loader against the pile or windrow it is to pick up, which combines the advantages of past crowder drives, such as extremely slow speed and uniformity of speed, with other advantages such as cornplete freedom from dangerously high torques, easy adjustability of crowding speed and easy reversing at a higher speed regardless of the speed for which the crowding drive is set.

This is accomplished in accordance with the present invention in an exceedingly simple manner. The traction wheels are driven for crowding by a hydraulic motor, the hydraulic fluid for which is supplied by a pump driven by the engine. The pressure available from the pump is limited, as by a pressure-relief valve, so that the application of a dangerously high torque to the drive shafts is positively prevented. However, the pump pumps the driving fluid at a constant rate suitable for the maximum crowding or reverse speed desired. A manually controlled valve shifts the supply of driving liquid from the forward or crowding line to the reverse line. The crowding line is connected to the oil reservoir by a bypass which includes an adjustable flow control valve. Adjustment of this valve controls the forward or crowding speed by by-passing a predetermined amount of the constant supply of oil from the pump. The setting of this valve is not altered by operation of the reverse ers such as that shown in Fig. l.

'ice

valve to reverse at a higher speed and then advance again at the selected speed.

Additional objects and advantages of the invention will be apparent from the following description and from the drawings in which:

Figure 1 is a perspective view of one type of loader for which the present invention is especially suitable.

Fig. 2 is a schematic view of the drive of this invention and some associated apparatus.

Fig. 3 is a developed view of a gear box suitable for use in conjunction with this invention.

Fig. 4 is a fragmentary diagrammatic view showing a type of mounting for scraper blade or moldboard for which the present invention is exceptionally suitable.

Although the law requires a full and exact description of at least one form of the invention, such as that which follows, it is, of course, the purpose of a patent to cover each new inventive concept therein no matter how it may later be disguised by variations in form or additions of further improvements; and the appended claims are intended to accomplish this purpose by particularly pointing out the parts, improvements or combinations in which the inventive concepts are found.

The invention is especially suitable for traveling load- In this type of loader a first material handling device 11 moves the material to be loaded onto the lower end of an inclined endless belt conveyor 12, the upper end of which is positioned to extend over a truck following the loader. The first material handling means 11 is usually either a bucket conveyor as shown or a series of scraping blades similarly carried by endless chains. For convenience, this first material handling means may be called a digging conveyor, whether of the bucket or scraper type, and the conveyor 12 may be called a belt conveyor or a loading conveyor.

Loaders of this type are used mostly on highways, to pick up material which has been scraped into a windrow along the side of the road. It is apparent therefore that the loader must move forward continuously. Of course the forward movement during loading is quite slow and is often called creeping or crowding. The term crowding is especially apt because this forward movement crowds the digging conveyor against the windrow. The crowding movement is accomplished through traction wheels 14, usually the rear wheels, steering being accomplished by the front wheel 16.

Loaders of the illustrated type are provided with very powerful engines capable of driving the two conveyors and also capable of moving the vehicle along the highway at relatively high speed to the site of its operation. Heretofore the crowding drive has been accomplished by coupling this powerful engine to the traction wheels through a gearing of such extreme ratio that on occasion the axle shaft was likely to be twisted off, as already explained.

According to the present invention, a much more satisfactory crowding drive is provided, still using the power available from the main engine. This new crowding drive is represented diagrammatically in Fig. 2. From this figure it is seen that a special gear box 21 is connected to the engine 22 through a conventional transmission 23, which, according to standard practice, is a variablespeed transmission. As seen best in Fig. 3, the gear box or special transmission is driven by shaft 24 which may extend into the transmission or a shaft connected therewith. Through means to be described, the shaft 24 may be connected either to the wheel drive shaft 26 or to the pump drive shaft 27. In the latter event it drives hydraulic pumps 28 and 29. Likewise, the wheel drive shaft may be connected through intermediate gearing to a shaft 31 which is driven by fluid motor 32.

Hydraulic crowding drive The hydraulic pump 28 is preferably a positive displacement type so that it will pump a uniform volume of oil while driven at a constant speed. The term oil may be used to designate any suitable liquid for hydraulic drive purposes. The pump 23 has its input port connected to an oil reservoir 33. Its discharge port is connected to a relief valve 34 adjusted and connected to limit the oil pressure in feed line 36 to a safe value incapable of damaging parts such as the axle shafts. if this pressure is exceeded at the discharge of pump 23, some of the oil is released by relief valve 34 to return to the reservoir 33 through line 37. Of course the various oil lines herein referred to may be any suitable type of conduit, either piping or high pressure hose. The feed line 336 communicates with a reversing valve 33 operated by a lever 39. The lever 39 is positioned or provided with a remote control means to be conveniently operable manually by a driver in cab 4-1. Either a foot lever or a hand lever may be used. With the lever 39 in one position, feed line 36 is connected with forward feed line 42, the line 43 being simultaneously connected to return line 44 communicating with oil reservoir 33. Under these conditions the fluid motor 32 is driven forwardly and in turn drives the traction wheels 1 forwardly to crowd the loader against the material to be loaded.

When the lever 39 is in the opposite position, the connections to motor 32 are reversed and feed line 36 is connected to reverse line 43, the forward feed line 42 being connected to return line 44. With these connections the fluid motor 32 is driven in reverse direction and drives wheel 14 in reverse direction.

With such valves, there is commonly and perhaps inevitably an intermediate position in which there is no how of fluid to the motor.

During loading operations the engine 22 preferably rotates at a fairly constant speed high enough for efficient development of power. The speed of crowding should not be altered by varying the engine speed because the engine speed should remain constant for driving the conveyors it and 12 at constant speed. Nevertheless it is desirable that the crowding speed be subject to delicate adjustment preferably with a high dependability of any selected speed. According to the present invention this is accomplished by connecting a variable flow control valve 46, perhaps more accurately called a rate of flow control valve, to the forward feed line 42. The valve 46 is preferably connected as a by-pass between the forward feed line and the return line 44. It may be adjusted by a lever 47 to vary the rate of flow of oil through the by-pass line The lever 7 may be manually operatcd by a driver in cab 41. With a constant speed of delivery of oil from pump 25, it is apparent that the speed of forward drive of fluid motor 32 will be accurately determined by the setting of ever 4-7 on valve to pro vide a predetermined constant diversion of the constant rate of supply.

Thus with any particular setting of the lever 4-7 the oil flowing through by-pass line 43 will be constant and hence the oil which remains to fiow through forward feed line 42 and drive id id engine 32 will be constant. Accordingly the forward feed will be constant with the exception that if a firm obstruction is encountered the forward movement will stop, the excess oil then resulting being divested by pressure relief valve 34 directly to the oil reservoir Although the flow control valve 4-6 could be connected directly in the forward feed line 42 instead of in the bypass line 48, this would be less efficient hydraulically. The maximum pressure would be maintained behind it whenever it was restraininz the flow.

The flow control valve has no effect on the reverse drive. In this instance the reverse line 43 is connected directly to the feed line 36 and the forward feed line 42 is connected d rectly without restraint to the return line 44. This is desirable because there is no reason to back away at the extremely slow speeds sometimes used for crowding. The maximum crox-vding speed is suitable for reverse whenever the crowding movement has been carried too far or is blocked by a firm obstruction. Thus the lever 47 may be set at the position which along a particular windrow appears to give the proper crowding speed, and this crowding speed will be maintained in spite of occasional reversals at a higher speed. If the digging conveyor 11 begins to stall the driver may shift lever 39 momentarily for a quick backing away and then shift it again for resuming the same forward speed previously used. Of course he may also easily shift the lever 47 to slightly reduce the forward speed if this seems appropriate. The drive for digging conveyor 11 preferably includes a slip device which permits it to stall under predetermined load conditions without stalling the engine.

The valve 33 preferably has a neutral position so that when the driver anticipates that a stalling condition is about to be encountered he can merely shift lever 39 to the neutral position to discontinue the crowding movement. Preferably in the neutral position of valve 38, feed line 36 is connected to return line 44.

Although the various hydraulic units indicated may be of any form, it may be helpful to indicate types which have been found satisfactory. The pump and motor are, respectively, type QHlZ and MHZSS of the Gerotor May Corporation. The flow control valve 46 is type FYZOZC of the VlClQBTS Corporation adjustable between minimum and maximum rates of flow of 15 and 3,450 cubic inches per minute. Preferably its maximum flow should be as great or approximately as great as the output of pump 28 when the latter is operated at the normal speed at which the engine is operated for driving the conveyors 11 and 2-. The form of flow control valve indicated should be provided with a drain line 49. A suitable adjustment for the safety or relief valve 34 has been found to be 1,500 lbs. per square inch.

Although the drive within gear box 21 may be considerably varied, or its equivalent incorporated within transmission 23, it is noted that the form of gear box shown in Fig. 3 has been found satisfactory. Fig. 3 is a developed view, the box being somewhat more compact than would be apparent from this view. One difference is that the shafts 25 and 24 have been shown in the same horizontal plane on which the section is taken when in fact one is displaced from this plane ninety degrees about the other.

The pumps 28 and 29 and their shaft 27 are controlled by gear The gear wheel 51 is controlled by a shift rod 52- so that it may engage drive gear 53 or be shifted to the neutral position shown in Fig. 3. It cannot be shifted further to the left in Fig. 3, movement being limited by shoulder 54 on shift rod 52.

The wheel drive shaft 26 carries a shiftable gear wheel 56 controlled by shift rod 57. In the position illustrated in Fig. 3, the gear wheel 56 is driven by shaft 31 driven by a fluid motor 32. The drive extends from pinion 58 through gear 55 and its rigidly associated pinion 61 to gear 62 and its rigidly associated pinion d3 which meshes with gear 56. By operation of rod 57 gear 56 may be shifted through a neutral position to engage gear 53. Thus in the latter position the traction wheels will be driven by an all-mechanical drive, whereas with gear 56 in the position illustrated the traction wheels may be driven by the hydraulic motor 52.

Fixed on shaft 24 is a sprocket or a double sprocket 66 which through a chain drive may drive sprocket 67 to drive shaft 63, which in turn drives the conveyors 11 and 12.

Hydraulic pump 29 may be used to drive auxiliary devices such as hydraulic cylinders for raising conveyors 11 and 12.

The bearings used in the gear case 21 for the various rotating parts are ball bearings throughout.

The crowding drive of this invention appears to have an additional advantage when the type of structure diagrammatically illustrated in Fig. 4 is used. Here a gathering scraper 71 slides along the ground, being connected to chassis 72 of the loader vehicle by a toggle member 73. The toggle member 73 slopes downwardly and forwardly so that when the scraper 71 is raised by cable means diagrammatically indicated at 74 substantial clearance above the road may be obtained. It is preferred that the cable means 74 be slack ordinarily so that the scraper 71 is free to rest on the ground. As a result, there is a tendency when scraper 71 strikes an obstruction for the toggle member 73 to cause a buckling action by swinging clockwise about its rear pivot. This would either raise the chassis 72 or cause the rear end of the scraper 71 to dig into the ground. Objectionable results along this line are avoided by the crowding drive of this invention in which the driving force is limited by the relief valve 34. It may be noted in this connection that the valve 34 is preferably readily adjustable, a gauge 76 being located in cab 41 to aid in its adjustment.

I claim:

1. A mobile loader including loading conveyor means, a vehicle carrying said conveying means and including traction means, an engine for driving the conveying means and the traction means, a hydraulic positive displacement pump, means optionally eifective for connecting the hydraulic pump to the engine to be driven thereby, a hydraulic motor, means for optionally conmeeting the traction means either to the hydraulic motor or to the engine independently of said motor, and

means for hydraulically connecting said pump to said motor to drive the motor including means for limiting the oil pressure supplied to the motor, a reversing valve and a separate adjustable rate of fiow control valve connected to the forward drive connection of the motor in by-pass relationship to the motor.

2. A mobile loader including loading conveyor means, a vehicle carrying said conveying means and including traction means, an engine for driving the conveying means and the traction means, a hydraulic pump, means optionally effective for connecting the hydraulic pump to the engine to be driven thereby, a hydraulic motor, means for optionally connecting the traction means either to the hydraulic motor or to the engine independently of said motor, and means for hydraulically connecting said pump to said motor to drive the motor including means for limiting the oil pressure supplied to the motor, a reversing valve and a separate adjustable rate of flow control valve connected to the forward drive connection of the motor to control the rate of flow to the motor during forward drive of the motor.

3. A mobile loader including loading conveyor means, a vehicle carrying said conveying means and including a drivers cab and traction means, an engine for driving the conveying means and the traction means, a hydraulic positive displacement pump, means optionally effective for connecting the hydraulic pump to the engine to be driven thereby, a hydraulic motor, means for optionally connecting the traction means either to the hydraulic motor or to the engine independently of said motor, and means for hydraulically connecting said pump to said motor to drive the motor including means for limiting the oil pressure supplied to the motor, a reversing valve and a separate adjustable rate of flow control valve connected to the forward drive connection of the motor necting the traction means either to the hydraulic motor or to the engine independently of said motor, and means for hydraulically connecting said pump to said motor to drive the motor including means for limiting the oil pressure supplied to the motor, a reversing valve and adjustable rate of flow control valve means connected to the forward drive connection of the motor to control the rate of flow to the motor during forward drive of the motor.

5. Driving mechanism for propelling a vehicle equipped with traction wheels, an engine-driven variable speed transmission, and mechanism for digging and loading material while the vehicle is propelled comprising: selectively controlled gearing driven by the variable speed transmission for driving the traction wheels, a hydraulic motor, a pump selectively driven by the gearing driven by the variable speed transmission, for supplying fluid under pressure to drive the hydraulic motor, gearing for selectively driving the traction wheels from the hydraulic motor, means for selectively controlling the operation of the gearing for driving the traction wheels from the transmission, means for controlling the operation of the hydraulic motor for driving the traction wheels and means for selectively controlling the operation of the pump.

6. Driving mechanism for propelling a vehicle equipped with traction wheels, an engine-driven variable speed transmission, and mechanism for digging and loading material while the vehicle is propelled comprising: selectively controlled gearing driven by the variable speed transmission for driving the traction wheels, a hydraulic motor, a pump selectively driven by the gearing driven by the variable speed transmission, for supplying fluid under pressure to drive the hydraulic motor, speed reducing gearing for selectively driving the traction wheels from the hvdraulic motor and means for selectively controlling the operation of the gearing for driving the traction wheels from the transmission, means for controlling the operation of the speed reducing gearing by the hydraulic motor for driving the traction wheels, and means for selectively controlling the operation of the pump.

7. A driving mechanism in accordance with claim 6 in which a pressure relief valve is connected to limit pressure of the fluid supplied by the pump to the hydraulic motor, whereby the torque output of the speedreducing gearing is limited, as a safeguard against breakage.

8. Driving mechanism for propelling a vehicle equipped with traction wheels, an engine-driven variable speed transmission, and mechanism for digging and loading material while the vehicle is propelled comprising: selectively controlled gearing driven by the variable speed transmission for driving the traction wheels, a reversible hydraulic motor, a pump selectively driven by the gearing driven by the variable speed transmission for supplying fluid under pressure to drive the hydraulic motor, gearing for selectively driving the traction wheels from the hydraulic motor and means for selectively controlling the operation of the gearing for driving the traction wheels from the transmission, means for controlling the two-way operation of the hydraulic motor for driving the traction wheels, and means for selectively controlling the operation of the pump.

9. Driving mechanism for propelling a vehicle equipped with traction wheels, an engine-driven variable speed transmission, and mechanism for digging and loading material while the vehicle is propelled comprising: selectively controlled gearing driven by the variable speed transmission for driving the traction wheels, a hydraulic motor, a pump selectively driven by the gearing driven by the variable speed transmission, for supplying fluid under pressure to drive the hydraulic motor, gearing for selectively driving the traction wheels from the hydraulic motor, means for selectively controlling the operation of the gearing for driving the traction Wheels from the variable speed transmission, means for controlling the operation of the hydraulic motor for driving the traction wheels at different speeds, and means for selectively controlling the operation of the pump.

10. Driving mechanism for propelling a vehicle equipped with traction wheels, an engine-driven variable speed transmission and mechanism for digging and loading material while the vehicle is propelled comprising: selectively controlled gearing driven by the variable speed transmission for driving the traction wheels, a reversible rotary hydraulic motor, a pump selectively driven by the gearing driven by the variable speed transmission for supplying fluid under pressure to drive the hydraulic motor, gearing for selectively driving the traction wheels from the hydraulic motor, means for selectively controlling the operation of the gearing for driving the traction Wheels from the transmission, means for controlling the operation of the hydraulic motor for driving the traction wheels at different forward speeds and for reverse travel, and means for selectively controlling the operation of the pump.

11. Driving mechanism for propelling a vehicle equipped with traction wheels, an engine-driven variable speed transmission, and mechanism mounted on the front of the vehicle for digging and loading material while the vehicle is being propelled comprising: a shaft connected to be driven by the variable speed transmission, a second shaft connected to drive the traction wheels, a rotary hydraulic motor, a pump for supplying fluid under pressure for driving said motor, means for selectively driving the pump from said first mentioned shaft, means for selectively driving the second shaft from the first shaft, and selectively controlled speed reducing gearing for driving the second shaft from the hydraulic motor.

12. Driving mechanism for propelling a vehicle equipped with traction wheels, an engine-driven variable speed transmission, and mechanism mounted on the front of the vehicle for digging and loading material while the vehicle is being propelled comprising: a shaft connected to be driven by the variable speed transmission, a second shaft connected to drive the traction Wheels, a rotary reversible hydraulic motor, a pump for supplying fluid under pressure for driving said motor, means for selectively driving the pump from said first mentioned shaft, means for selectively driving the second shaft from the first shaft, selectively controlled speed reducing gearing for driving the second shaft from the hydraulic motor, and means for controlling the flow of fluid to the hydraulic motor, to reverse its operation.

1}. Auxiliary driving mechanism for propelling a vehicle equipped with traction wheels, an engine-driven variable speed transmission, digging mechanism mounted on the front of the vehicle, adapted to penetrate material as the vehicle is propelled, and means for loading the material, comprising: a shaft connected to be driven by the variable speed transmission, a second shaft connected to drive the traction Wheels, a rotary hydraulic motor, a pump for supplying fluid under pressure for driving said motor, gearing for selectively driving the pump from said first mentioned shaft, gearing for selectively driving the second shaft from the first shaft, and selectively controlled speed reducin gearing for driving the second shaft from the hydraulic motor.

14. Auxiliary driving mechanism for propelling a vehicle equipped with traction wheels, an engine-driven variable speed transmission, digging mechanism mounted on the front of the vehicle, adapted to penetrate material as the vehicle is propelled, and means for loading the material, comprising: a shaft connected to be driven by the variable speed transmission, a second shaft connected to drive the traction wheels, a rotary reversible hydraulic motor, a pump for supplying fluid under pressure for driving said motor, gearing for selectively driving the pump from said first mentioned shaft, gearing for selectively driving the second shaft from the first shaft, selectively controlled speed reducing gearing for driving the second shaft from the hydraulic motor, and means for controlling reverse flow of the hydraulic fluid for reverse operation of the hydraulic motor.

15. An auxiliary driving unit for propelling a vehicle equipped with traction wheels, an engine-driven variable speed transmission, digging mechanism on the front of me vehicle adapted to penetrate material as the vehicle is propelled, and loading means for the material, comprising: a case, a first shaft mounted in the case and connected to be driven by the variable speed transmission, a second shaft in the case connected to drive the traction wheels, a rotary reversible hydraulic motor mounted on the case, a pump mounted on the case for supplying fluid under pressure for driving said motor, gearing in the case for selectively driving the pump from said first shaft, selectively controlled gearing for driving the second shaft from the st shaft, selectively controlled speed reducing gearing for driving the second shaft from the hydraulic motor, and third shaft mounted in the case, driven by said ii at shaft; and means driven by said third shaft for driving the mechanism for digging and loading the material.

16. An auxiliary driving unit for propelling a vehicle equi ed with traction wheels, an engine-driven variable speed transmission, digging mechanism on the front of the vehicle adapted to penetrate material as the vehicle is pro elled, and loading means for the material, comprising: a case, a shaft mounted in the case and connected to be driven by the variable speed transmission, a second shaft in the case connected to drive the traction wheels, a rotary reversible hydraulic motor mounted on the case, a pump mounted on the case for supplying fluid under pressure for driving said motor, gearing in the case for selectively driving the pump from said first mentioned shaft, gearing for selectively driving the second shaft from the first shaft, and selectively controlled speed reducing gearing for driving the second shaft from the hydraulic motor, a third shaft mounted in the case, sprockets and a chain for driving the third shaft from said first shaft; and means driven by said third shaft for driving the mechanism for digging and loading the material.

17. An auxiliary driving unit for propelling a vehicle equipped with traction Wheels, an engine-driven variable speed transm-ission, digging mechanism on the front of the vehicle adapted to penetrate material as the vehicle is propelled, and loading means for the material, comprising: a case, a first shaft mounted in the case and connected to be driven by the variable speed transmission, a gear fixed on said first shaft, a second shaft in the case connected to drive the traction wheels, a rotary hydraulic motor mounted on the case, a pump mounted on the case for supplying fluid under pressure for driving said motor, gearing for selectively driving the pump from the first shaft, a slidable gear rotatable with the second shaft, shiftable to engage the gear fixed on the first shaft, for driving the second shaft from the first shaft, and speed reduction gearing for driving the second shaft from the hydraulic lOfGl' including a gear rotatable on the first shaft, a gear rotatable on the second shaft, a shaft driven by the hydraulic motor provided with a gear engaging the gear rotatable on the second shaft, the slidable gear on the second shaft being shiftable to engage the gear rotatable on the first shaft.

18. An auxiliary driving unit for propelling a vehicle equipped with traction Wheels, an engine-driven variable speed transmission, digging mechanismon the front of the vehicle adapted to penetrate material as the vehicle is propelled, and loading means for the material, comprising: a case, a first shaft mounted in the case and connected to be driven by the variable sped transmission, a gear fixed on the first shaft, a second shaft in the case connected to drive th traction wheels, a rotary hydraulic motor mounted on the case, a pump mounted on the case for supplying fluid under pressure for driving said motor, means for selectively driving the pump from the first shaft, a slidable gear rotatable with the second shaft shiftable to engage the gear fixed on the first shaft for driving the second shaft from the first shaft and speed reduction gearing for driving the second shaft from the hydraulic motor including a pair of gears rotatable on the first shaft, a pair of gears rotatable on the second shaft, a shaft driven by the hydraulic motor provided with a gear engaging one of the gears rotatable on the second shaft, the slidable gear on the second shaft being shiftable to engage one of the gears rotatable on the first shaft.

19. Driving mechanism for propelling a vehicle equipped with an engine-driven variable speed transmission and mechanism for digging and loading material as the vehicle is propelled comprising: selectively con trolled gearing driven by the variable speed transmission for driving the traction Wheels; a rotary reversible hydraulic motor, a pump selectively driven by the gearing driven by the variable speed transmission for supplying fluid under pressure to drive the hydraulic motor, gearing for selectively driving the traction Wheels from the hydraulic motor, means for selectively controlling the operation of the gearing for driving the traction wheels from the transmission; and means for controlling the operation of the hydraulic motor including valve-means for controlling the two-way flow to the hydraulic motor and to cut off the flow to the motor, and a handle for operating said valve means.

20. Driving mechanism for propelling a vehicle equipped with an engine-driven variable speed transmission and mechanism for digging and loading material as the vehicle is propelled, comprising: selectively controlled gearing driven by the variable speed transmission for driving the traction wheels; a rotary reversible hydraulic motor, a pump selectively driven by the gearing driven by the variable speed transmission for supplying fluid under pressure to drive the hydraulic motor, gearing for selectively driving the traction wheels from the hydraulic motor, means for selectively controlling the operation of the gearing for driving the traction Wheels from the transmission; and means for controlling the operation of the hydraulic motor including valve means for controlling the two-way flow to the hydraulic motor and to cut off the flow to the motor; a remote control handle for operating said valve means, a rate-of-flow control valve for the fluid between the valve means and the motor, and a remote control handle for shifting the rate-of-flow control valve.

21. Driving mechanism for propelling a vehicle equipped with an engine-driven variable speed transmission and mechanism for digging and loading material as the vehicle is propelled, comprising: selectively controlled gearing driven by the variable speed transmission for driving the traction wheels; a rotary reversible hydraulic motor, a pump selectively driven by the gearing driven by the variable speed transmission for supplying fluid under pressure to drive the hydraulic motor, gearing for selectively driving the traction wheels from the hydraulic motor, means for selectively controlling the operation of the gearing for driving the traction wheels from the transmission; and means for controlling the operation of the hydraulic motor including valve means for controlling the two-way flow to the hydraulic motor and to cut off the flow to the motor; a remote control handle for operating the valve means, a rate-of-flow control valve for by-passing fluid from the valve means, and a remote control handle for shifting the rate-of-flow control valve.

22. Driving mechanism for propelling a vehicle equipped with an engine-driven variable speed transmission and mechanism for digging and loading material as the vehicle is propelled, comprising: selectively controlled gearing driven by the variable speed transmission for driving the traction Wheels; a rotary reversible hydraulic motor, a pump for supplying fluid under pressure to the motor, gearing selectively driven by the gearing driven by the variable speed transmission for operating the gump, gearing for selectively driving the traction wheels from the hydraulic motor, means for selectively controlling the operation of the gearing for driving the traction wheels from the transmission; and means for controlling the operation of the hydraulic motor including valve means for controlling the two-way flow of fluid to the hydraulic motor and to cut off the flow to the motor; and a remote control handle for operating the valve means, and a remote control means for controlling the gearing for driving the pump.

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